It has been proposed heretofore to convert the reaction gases of the CLAUS process which contain hydrogen sulfide (H.sub.2 S) and sulfur dioxide (SO.sub.2) to elemental sulfur and water vapor in catalyst beds, thereby removing the two sulfur compounds and recovering sulfur in an elemental state which is a desirable product.
It is desired to obtain a high yield of high purity sulfur from such processes.
The reaction proceeds in accordance with the equation EQU 2H.sub.2 S+SO.sub.2 .fwdarw.3S+2H.sub.2 O+Q.
The products of the reaction, as can be seen from the equation, are elemental sulfur and water, Q being the liberated heat. Since such processes tend toward a state of equilibrium (i.e. the competing reaction in which elemental sulfur combines with water to produce hydrogen sulfide and sulfur acid becomes significant), the reaction is generally carried out in a plurality of stages.
Since the reaction is highly exothermic, as is indicated by the evolution of heat Q, the reaction gases must be cooled after they have traversed the catalyst body so that condensation of sulfur and, if desired, water, is brought about and the sulfur is recovered. However, in conventional systems this requirement is disadvantageous since the cooling is effected significantly below the desired reaction temperature and even below the activation temperature at which the elemental-sulfur-forming reaction will proceed. Consequently, the gases must be reheated between the catalyst stages, i.e. before the reaction gas is introduced into the next stage. Such sequences of catalytic reaction, cooling, reheating, catalytic reaction . . . are repeated several times to maximize the yield of elemental sulfur.